The present invention relates to a semiconductor device; and, more particularly, to a method for manufacturing a gate structure incorporated therein aluminum oxide as a gate dielectric.
As is well known, a semiconductor device has been down-sized by a scale down of a design rule. Therefore, a gate oxide tends to rapidly approach 30 xc3x85 in thickness and below to increase the capacitance between a gate electrode and a channel region. However, the use of silicon dioxide as a gate dielectric is limited at this thickness and below. Once silicon dioxide SiO2 is formed to a thickness of less than 30 xc3x85, direct tunneling may occur through the gate dielectric to the channel region, thereby increasing a leakage current associated with the gate electrode and the channel region, causing an increase in power consumption.
Since reducing the thickness of the gate dielectric inherently increases the gate-to-channel leakage current, alternative methods have been developed to reduce this leakage current while maintaining thin SiO2 equivalent thickness. One of these methods is to use a high K dielectric material such as Ta2O5 as the gate dielectric material to increase the capacitance between the gate and the channel.
However, if a poly-silicon is utilized as a gate electrode, the use of Ta2O5 for gate dielectric materials has a disadvantage in integrating the semiconductor device. That is, an undesired SiO2 and TaSi2 are formed at an interface between Ta2O5 and the poly-silicon, which, in turn, increases an equivalent oxide thickness. In order to overcome this problem, a barrier metal such as TiN is employed. However, the TiN makes a threshold voltage shift changed.
In addition, the use of high K dielectrics for gate dielectric materials is disadvantageous in integrated circuits because high dielectric materials contain great number of bulk traps and interface traps than gate dielectrics made from thermally grown SiO2. These traps adversely effect sub-threshold slope and threshold voltage operation of electric devices.
If the above-described problems are overcome, a high K dielectric is utilized as a gate oxide with excellent leakage current as well as a low interface state with both a gate electrode and a silicon substrate.
It is, therefore, an object of the present invention to provide a method for manufacturing a gate structure incorporated therein aluminum oxide as a gate oxide for use in a semiconductor device.
In accordance with one aspect of the present invention, there is provided a method for manufacturing a gate structure for use in a semiconductor device, the method comprising the steps of: a) preparing a semiconductor substrate provided with an isolation region formed therein; b) forming an aluminum oxide (Al2O3) layer on top of the semiconductor substrate with doping a dopant in situ; c) forming a conductive layer on top of the Al2O3 layer; and d) patterning the conductive layer, thereby obtaining the gate structure.
In accordance with another aspect of the present invention, there is provided a method for method for manufacturing a gate structure for use in a semiconductor device, the method comprising the steps of: a) preparing a semiconductor substrate provided with an isolation region formed therein; b) forming an Al2O3 layer on top of the semiconductor substrate; c) forming a conductive layer on top of the Al2O3 layer; d) implanting dopants into the Al2O3 layer; e) patterning the conductive layer and the Al2O3 layer into the gate structure; and f) selectively reoxidizing the dopants.